INSTRUCTIONS FOR THE SETTING, TESTING AND COMMISSIONING OF

MOTOR PROTECTION RELAYS

1 .

IMM 7900 RELAY FUNCTIONS

2.

RELAY DESCRIPTION

2.1

Digital display

2 .2

Nomenclature of the symbols used on the face-plate

2.3

Operating curves and block drawing

3.

RELAY SETTINGS

3 .1

How to select suitable settings

4.

RELAY CHECKING AND COMMISSIONING

4.1

Recommendations

4.2

Pre-commissioning checks

4.2.1 Thermal unit at twice setting

4.2.2 Short-circuit (threshold and operating time) and

unbalance (operating curve)

4.2.3 Earth fault (threshold and operating time)

4.2.4 Starting characteristic and locked rotor

4.2.5 Starts frequency limitation

4.2.6 Undercurrent

4.2.7 Communications

4.3

Commissioning

5.

ANNEX

5.1

Testing a 60Hz relay on a 50Hz supply

5.2

Checking the thermal characteristics

This manual only applies to IMM 7960 relays, drawing 25A4, and to 1MM 7990

relays, drawing 9987 .

2

The IMM 7960 and 7990 series of relays have been specifically designed to ensure the

electrical protection of high voltage and large low voltage motors .

The digital display provides a readout of certain important data . See table n 1 for the

list of the different elements .

Passing from one code valuee to the next is achieved by pressing the push-but ton

If this push button is held down, the displayed value corresponds to the value of the

setting . After releasing the push-button a new value appears, corresponding to a

measured or calculated value .

3

4

5

6

7

8

9

10

1 1

1 2

13

14

If the test equipment does not incorporate an automatic tripping system, it is advisable to

stop the current injection as soon as the expected result is obtained .

15

1 6

17

1 8

19

20

21

22

23

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